Dimethenamid Synthesis Essay

1. Introduction

Hypochlorous acid (HOCl) and hypobromous acid (HOBr) are microbicidal agents produced when the white blood cells, neutrophils and eosinophils, respectively, are challenged by stimuli like bacteria and fungi [1]. Eosinophils, in particular, are associated with the host defense against parasitic helminth infections and asthma exacerbation [2,3]. These halogenating and oxidizing agents also play an important role in tissue damage associated with chronic inflammatory diseases [4,5]. For instance, eosinophilia, a characteristic of asthmatic subjects [6] has been associated with an increased level of 3-bromotyrosine, a biomarker of the damaging effects of HOBr [7].

The formation of these oxidants is due to the large amount of the enzymes myeloperoxidase (MPO) and eosinophil peroxidase (EPO) in these cells, which promote the catalytic oxidation of chloride (Cl−) and bromide (Br−) to HOCl and HOBr, respectively [8,9]. The catalytic mechanism involves the transient production of the redox active compounds, named compound I (MPO-I and EPO-I), which are two electron oxidized compared with the native enzyme. An important difference between MPO-I and EPO-I is their standard reduction potential [10]. Thus, while MPO-I (1.16 V) is able to oxidize efficiently both Cl− and Br− [11]; EPO-I (1.09 V) shows a large preference for Br− [12]. This chemical feature, the higher plasma level of Cl− (~100 mM) compared with Br− (~100 µM), and the higher oxidant capacity of HOCl (1.28 V) compared with HOBr (1.13 V) [13], could suggest that the biological effect of HOBr would be irrelevant compared with HOCl. However, this does not seem to be the case, since there is significant evidence that HOBr is more reactive with several biomolecules compared to HOCl [14,15]. This phenomenon is the consequence of the higher electrophilicity of HOBr compared to HOCl [16].

Taurine bromamine (Tau-NHBr) is a chemical produced by the reaction between HOBr and the non-essential amino acid taurine. Yazdanbakhsh et al. provided the first application of Tau-NHBr and proposed its endogenous formation [17]. These authors found that stimulated eosinophils could be a source of Tau-NHBr, since these cells may produce HOBr, and taurine is abundantly present in leukocytes. It is interesting to note that this finding took place just one year after the discovery that eosinophils could produce and release HOBr [18].

Currently, Tau-NHBr is used as an anti-inflammatory and a topical antimicrobial drug. Some examples of its applications are its use as a therapeutic agent for the treatment of acne vulgares [19,20]; treatment of biofilm-associated infections on dental surfaces caused by Pseudomonas aeruginosa [21,22]; microbicidal activity against Escherichia coli and Staphylococcus aureus at insensitive body regions with low organic matter [23]; inhibition of the production of inflammatory mediators, such as prostaglandin E2 (PGE2), nitric oxide (NO) and pro-inflammatory cytokines [24]; and inhibition of degradation of TNF-α-induced Nuclear Factor-kappaB activation in Jurkat cells and myeloid-committed eosinophils [25]. The equivalent chlorinated haloamine is taurine chloramine (Tau-NHCl), which is the reaction product of the interaction between taurine and HOCl. Tau-NHCl is produced by activated neutrophils and released at inflammatory sites, inhibiting the production of inflammatory mediators [26]. An important chemical feature of Tau-NHCl, which makes this compound so interesting and extensively studied, is its mild oxidant capacity compared to its precursor HOCl. Thus, Tau-NHCl is able to oxidize selectively sulfhydryl residues in proteins [27], and to act as an endogenous antioxidant [28]. These aspects might be involved in the signaling pathways susceptible to Tau-NHCl [29,30]. There are also a large number of applications for Tau-NHCl as a topical anti-inflammatory and anti-infective drug [31].

In contrast to Tau-NHCl, for which the chemical properties have been intensively studied [32], much less is known about Tau-NHBr. This was our motivation for undertaking this study. Here, the reactivity of Tau-NHBr was evaluated and compared with HOBr, HOCl and Tau-NHCl, using several endogenous and non-endogenous chemicals. Using fast kinetic techniques, it was possible to measure the bimolecular rate constants of these reactions. We believe that this chemical data will be helpful for those interested in the application of this interesting compound.

2. Results and Discussion

2.1. Preparation and Stability of Tau-NHBr

Tau-NHBr can be prepared by reacting HOBr with taurine (Equation 1). However, it exists in equilibrium with its dibromamine form (Tau-NBr2) and, as has been demonstrated by Thomas et al., pure Tau-NHBr is only obtained using a large excess of taurine. In our studies, we usually prepare stock solutions of Tau-NHBr by reacting 5 mM HOBr with 500 mM taurine in 50 mM phosphate buffer, pH 7.0, i.e., a 100-fold excess of taurine. This solution was very stable when stored in the refrigerator and lost less than 20% of its initial concentration after five weeks [33].

2.2. Reactivity with Tryptophan

Aiming to obtain a comprehensive knowledge of the chemical reactivity of Tau-NHBr, we used endogenous and non-endogenous compounds as potential targets. The first target was tryptophan, whose reactivity with HOCl and HOBr has been described [34,35]. Figure 1a shows the time-dependent fluorescence decay of tryptophan by the addition of Tau-NHBr. In these experiments, the concentration of tryptophan was kept constant at 25 µM and the concentration of Tau-NHBr was varied from 100 to 500 µM. From this pseudo-first-order experimental condition, the apparent second-order rate constant (k2) was calculated (7.7 × 102 M−1s−1, Figure 1b). To gain insight into the significance of this value, it was compared with those obtained using HOBr, HOCl and Tau-NHCl. Figure 1a shows that, whereas 150 µM Tau-NHBr provoked the tryptophan fluorescence decay in about 20 s, HOBr caused the same effect in less than 0.02 s (Figure 1c). Unfortunately, this reaction was too fast to determine k2; however, its higher reactivity compared to Tau-NHBr was evident. Regarding HOCl, we took as reference a recent determination performed in our laboratory using exactly the same analytical protocol (k2 = 8.1×104 M−1s−1) [15]. Finally, and in agreement with the well-known low reactivity of Tau-NHCl [31], we found that this haloamine was unreactive with tryptophan. In fact, the experiments were done using up to a 10-fold excess of Tau-NHCl compared with Tau-NHBr, but no indication of consumption of tryptophan was observed for up to 10 min. From these results, the following reactivity sequence was obtained: HOBr > HOCl > Tau-NHBr > Tau-NHCl (unreactive).

2.3. Reactivity with Dansylglycine

In contrast to tryptophan, which has significant intrinsic fluorescence, other oxidizable amino acids, like methionine and cysteine, are not fluorescent. Tyrosine is also fluorescent, but with its maximum excitation/emission at 280/305 nm, our application of a stopped-flow system coupled to a LED source (280 nm) and the emission cut-off filters (305 nm) made the determination of k2 unworkable. Thus, instead of a direct measurement of the reaction rate, an indirect procedure was performed by comparing the effect of these amino acids with the reaction rate of dansylglycine and Tau-NHBr. Dansylglycine is a fluorescent probe used for attribution of binding sites in albumin [39]. This probe was selected for several reasons, including our previous determination of its bimolecular rate constant with HOBr and HOCl [15], its fluorescence properties (λex 360 nm, λem 550 nm), which made the spectral interference of the studied compounds minimal, and its application as a probe for tryptophan residues in albumin, as will be demonstrated below.

Before the use of dansylglycine for the comparison of the reactivity of these amino acids, the measurement of its apparent second-order rate constant with Tau-NHBr was performed (Figure 3). Corroborant with the tryptophan results, the obtained k2 (9.5 × 101 M−1s−1) was significantly lower than for HOBr (7.3 × 106 M−1s−1) and HOCl (5.2 × 102 M−1s−1) [15]. Tau-NHCl was totally unreactive with dansylglycine. The following reactivity sequence again was established: HOBr > HOCl > Tau-NHBr > Tau-NHCl.

Following the analytical protocol established above, the selectivity of Tau-NHBr with the oxidizable amino acids was evaluated by measuring and comparing tryptophan, tyrosine, cysteine and methionine in regard to their efficacy as inhibitors of the oxidation of dansylglycine.

The results displayed in Figure 4 show the effect of tryptophan and tyrosine in the fluorescence bleaching of dansylglycine. It can be observed that, whereas tryptophan was an effective competitor and significantly inhibited the depletion of dansylglycine, tyrosine was much less effective. From these experiments, the relative reactivity of the amino acids was calculated as the slope of the curve (kobsversus amino acid concentration). The results were tryptophan 2.4 × 10−4 ∆kobs/mM (Figure 4b) and tyrosine 1.3 × 10−5 ∆kobs/mM (Figure 4d), showing that tryptophan was about an 18-fold better inhibitor, or, in other words, 18-fold more reactive with Tau-NHBr compared with tyrosine.

Following the same experimental concept, the effects of cysteine and methionine on dansylglycine bleaching were also measured. The slope of the curve of the pseudo first-order rate constant versus amino acid concentration was cysteine 8.7 × 10−5 ∆kobs/mM and methionine 6.5 × 10−5 ∆kobs/mM (Figure 5). Hence, the following sequence of relative reactivity of Tau-NHBr was established: tryptophan > cysteine ~ methionine > tyrosine.

2.5. Selectivity upon Tryptophan Residues in Proteins

As we have demonstrated above, Tau-NHBr has lower oxidant capacity compared to its precursor HOBr and HOCl. In this context, it is worth noting a principle of chemistry: lower reactivity usually implies greater selectivity. This principle seems to be applicable in our studies, because, in contrast to HOBr and HOCl, Tau-NHBr was able to oxidize tryptophan but not tyrosine. Following this idea, we suspect that our recent proposal for the selectivity of Tau-NHBr [40] and Tau-NBr2 [41] for tryptophan residues in albumin and lysozyme could be reinforced by these new findings. Thus, aiming to advance this proposal, dansylglycine was used to probe the depletion of tryptophan in human serum albumin (HSA).

Dansylglycine is a ligand of albumin. Its complexation can be monitored by an increased fluorescence quantum yield and a blue shift in the emission band, and, more importantly for our purpose, dansylated amino acids can be excited by fluorescence resonance energy transfer from tryptophan in HSA [42]. To make sure that this property is also applicable to dansylglycine, we added increasing concentrations of this compound to a fixed concentration of HSA. Our expectation was confirmed because dansylglycine was not fluorescent when excited at 295 nm; however, in the presence of HSA, the addition of increasing amounts of dansylglycine provoked a gradual quenching of the intrinsic fluorescence of the protein and a concomitant increase in the fluorescence of dansylglycine.

Considering these findings, dansylglycine was used as a probe for evaluation of the consumption of tryptophan in HSA provoked oxidation. In these experiments, the oxidation was provoked by adding a 20-fold excess of the oxidants and, after five minutes, methionine was added to deplete the excess of oxidants. The results depicted in Figure 6a confirmed our expectation of selectivity because, though much less reactive with free tryptophan, Tau-NHBr was more effective than HOCl or HOBr in depleting the intrinsic fluorescence of HSA, which is mainly due to tryptophan residues when excited at 295 nm [43]. In others words, Tau-NHBr seems to act mainly on tryptophan residues of the protein. Figure 6b shows the effect of the addition of dansylglycine after oxidation and depletion of the oxidant excess. The band at 485 nm was lower in the sample oxidized with Tau-NHBr, which is an additional confirmation that tryptophan residues were more efficiently oxidized using this oxidant, since the measured fluorescence was due to energy transfer from the tryptophan residues in HSA.

2.6. Comparison between Tau-NHCl and Tau-NHBr

As we have demonstrated above, Tau-NHCl was unreactive with all studied compounds in this work; which is, indeed, in agreement with its well-established poor oxidant capacity [32]. Obviously, it does not mean that Tau-NHCl is completely devoid of oxidant capacity, as is confirmed, for instance, by its capacity to oxidize sulfhydryl residues in proteins [27]. Tau-NHCl is also able to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) in acid medium, the chromogenic substrate used for determination of the chlorination activity of MPO [44]. Thus, aiming to quantify the difference in reactivity between Tau-NHBr and Tau-NHCl, we used TMB as the target. It must also be noted that instead of an acidic pH, the reaction was conducted at pH 7.0, as was used for the other compound studies in this work. It is important to emphasize this point, because its reactivity is significantly lower at neutral pH, which is, indeed, the reason for the application of acidic medium for determination of Tau-NHCl activity using TMB [44]. The results depicted in Figure 7

The word “synthesis” is defined as a combination of elements to form a connected whole. Thus, a synthesis essay definition is an essay that combines different ideas into a whole to prove a point (otherwise called the thesis). Often, it comes with a text that you should analyze.

Table Of Contents

Writing Process

A key factor of writing a synthesis essay is an analysis of a given text or a prompt. In order to successfully analyze it, you must comprehend the text’s purpose, rhetoric, and the argument that the author’s claim, in other words, you are answering the question: “So what?”. Then, you must build your own claim, and write an essay around that.

Most Common Topics

A synthesis essay prompt must be negotiable. Like in the EssayPro's example above, Andrew Jackson’s negative views on Native American people were widely supported, today, however, they would be appalling. Depending on your assignment, you may have to choose a primary text. Choose a text that might have opposing viewpoints.

Good topics would be ones that are debatable, for example:

Daylight savings

Minimum wage

Abortion

Immigration policy

Global warming

Gun control

Social media

How Do I Write A Thesis?

Once you pick a topic of your paper, read your sources and establish your position. Make sure you thoroughly analyze the sources and get a good understanding of them, structure your claim or argument and write your thesis.

Example: Andrew Jackson’s fear of the Native American “savages” reflects the prejudices and ideas of the colonist people in the Union and the Congress.*

How Do I Write An Outline?

Creating an outline will help maintain the structure of your paper. If your essay is split into three parts, split your outline into three chunks. Paste supporting evidence, sub-arguments, and specific points in the appropriate sections. Make sure that every point somehow proves the claim in your thesis. Extra information or tangents will only hinder your essay. However, if information goes against your central claim, then you should acknowledge it as it will make your essay stronger. Make sure you have read all of your sources. When writing about the sources, do not summarize them; synthesis denotes analysis, not plot-summary.

Example:

Introduction

Thesis

Main point 1

Main point 2

Main point 3

Body

Main point 1

Evidence (quote from a source)

Analysis of Evidence

Main point 2

Evidence (quote from a source)

Analysis of Evidence

Main point 3

Evidence (quote from a source)

Analysis of Evidence

Conclusion

Restate main points and answer unanswered questions

Read more about how to write a great INTRODUCTION

How Do I Format My Essay?

The format depends on what style is required by your teacher or professor. The most common formats are: MLA, APA, and Chicago style. APA is used by fields of Education, Psychology, and Science. MLA is used for citing Humanities, and Chicago style is used for Business, History, and Fine Arts. Purdue Owl is a format guide that focuses mainly on MLA and APA, and Easybib is a citation multitool for any of your external sources.

Some key points are:

Times New Roman 12 pt font double spaced

1” margins

Top right includes last name and page number on every page

Titles are centered

The header should include your name, your professor’s name, course number and the date (dd/mm/yy)

The last page includes a Works Cited

APA Format

Some key points are:

Times New Roman 12 pt font double spaced 1” margins

Include a page header on the top of every page

Insert page number on the right

An essay should be divided into four parts: Title Page, Abstract, Main Body, and References.

How do I write an AP English Synthesis Essay?

AP English Language and Composition is an extremely rigorous course that requires you to write essays that demonstrate deep understanding of the subject matter. In fact, if on the AP exam, your essay has perfect grammar and structure, you might still be awarded just 1 out of 9 points for not “defending, challenging, or qualifying your claim.” Sounds difficult, but it is doable. Before entering any AP class, it is best to read over the course overview and become familiar with the exam.

While writing, focus on the three branches of the AP English and Composition course: argument, synthesis, and rhetorical analysis.

Argument is the easiest component; create your claim and find specific supporting evidence. Convince your reader that you are right.

Synthesis requires you to read into multiple perspectives and identify an agreement and a disagreement between sources. This step is crucial to finding your own claim.

Rhetorical analysis deals with the author and his intentions. What was their purpose for writing this? Who is their intended audience? How does the author appeal to the audience and how does he structure his claim?

Essay Tips

There are two acronyms that are helpful with the three AP Lang writing branches.

Tip #1: SOAPS

Example text: Andrew Jackson’s speech to the Congress about sending Native Americans to the West.

Speaker: Identify the speaker of the piece, then analyze for bias and apply any prior knowledge that you have on the speaker.

Example: President Andrew Jackson had a bias against Native Americans. A piece written by Andrew Jackson about Native Americans will probably be written with a bias against him.

Occasion: Determine the time and the place of the written text, then identify the reason the text was written. Even if you aren’t sure of the reason, assume one and make your claim around it.

Example: Andrew Jackson was in office from 1829 to 1837. At this time, the Congress sent Native Americans to the West in order to clear the land for the colonists. Jackson was the one who made the proposal.

Audience: Who was the text directed to?

Example: Andrew Jackson’s speech was directed to a council.

Purpose: What is the text trying to say? Here, you analyze the tone of the text.

Example: Andrew Jackson appeals to pathos by calling Indians “savages”. His purpose is to portray Native Americans in a negative light, so the Congress passes the Indian Removal Act.

Subject: What is the main idea? What is the claim?

Example: Andrew Jackson wants the Congress to pass the Indian Removal Act because he believes Native Americans are uncultured and savage people.

Tip #2: Logos, Ethos, and Pathos

As you’ve probably learned before, Logos appeals to reason, Pathos appeals to emotion, and Ethos appeals to moral philosophy or credibility. However, for the AP Lang exam requires a wider understanding of the three.

If the text uses facts, statistics, quotations, and definitions, the speaker is appealing to Logos. Constituting various backup information is an extremely effective for people who want to persuade.

If the text uses vivid imagery and strong language it denotes Pathos, which is used to connect the audience to a piece emotionally; it is hardest to change the mind of a person who is linked to a subject via a strong emotion.

If the text attempts to demonstrate the speakers reliability or credibility, it is a direct appeal to Ethos. Using the example above, Andrew Jackson could have appealed to Ethos by stating the fact that he is the President of the United States, and thus, knows what is best for the union.

Often, Logos, Ethos, and Pathos lead to the use of logical fallacies.

Tip #3: DIDLS

This is a good shorthand for all textual analysis. While reading a text, try to pinpoint Diction, Imagery, Details, Language, and Sentence Structure in a piece. If anything stands out, add it to your analysis.

Rubric

High range essay (8-9 points)

Effectively develops a position on the assigned topic.

Demonstrates full understanding of the sources or text.

Correctly synthesizes sources and develops a position. The writer drives the argument, not the sources.

The writer’s argument is convincing.

The writer makes no general assertions and cites specific evidence for each point. His/her evidence is developed and answers the “so what?” question.

The essay is clear, well-organized, and coherent. It is a stand alone piece rather than an exam response.

Contains very few grammatical and spelling errors or flaws, if any.

Note: 8-9 essays are an extreme rarity. A strong ‘7’ paper can jump to an 8-9 if the writing style is mature and perceptive.

Middle-Range Essay (57)

Adequately develops a position on the assigned topic.

Demonstrates sufficient understanding of the ideas developed in sources

Sufficiently summarizes the sources and assumes some control of the argument. ‘5’ essays are less focused than ‘6’ and ‘7’.

The writer's argument is sufficient but less developed.

Writer successfully synthesizes the sources and cites them.

Writer answers the “So what?” question but may use generalizations or assertions of universal truth. Writer cites own experience and specific evidence.

Essay is clear and well organized. ‘5’ essays less so.

Contains few minor errors of grammar or syntax.

Note: A ‘7’ is awarded to papers of college-level writing. A ‘5’ on one of the AP English Language and Composition essays designates a 3 on the AP exam. It most likely relies on generalizations has limited control of the claim and argument. ‘5’ essays often lose focus and digress.

Low-Range Essays (1-4)

Inadequately develops a position on the assigned topic.

The author misunderstands and simplifies the ideas developed in the sources.

Over-summarizes the sources, lets the sources drive the argument.

Writer has weak control of organization and syntax. Essay contains numerous grammatical/spelling errors.

Writer does not cite the sources correctly, skips a citation, or cites fewer than the required minimum of the sources.

Notes: ‘4’ or ‘3’ essays do assert an argument but do not sufficiently develop it.

A ‘2’ essay does not develop an argument.

A 1-2 essay has severe writing errors and do not assert a claim.

Synthesis Essay Example

Essay Writing Advice From Our Professional Team

James Owen, online essay writer from EssayPro

The article reviews the basics of how to write a synthesis essay as well as how to dissect and analyze text when writing an AP English essay. One thing I would like to reemphasize is the importance of your thesis statement. When you write an essay for class or exam, make sure to state your argument clearly. If the reader of your essay doesn’t understand your point of view then what you’ve written is futile.

My advice is: when writing an essay in a short period (such as in an exam room) make sure to articulate your argument in every paragraph and connect every single one of your ideas to the thesis. My tip is to write your thesis down on a piece of paper and reread it at every point to ensure that the information applies and reinforces what you’ve stated in your thesis. This tip also goes for when you are writing a longer piece of writing, as it is very easy to lose focus and stray away from your main point.

Struggling With Writing an Essay?

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